1. Field of the Invention
The present invention relates to an ink jet recording head and an ink jet recording apparatus.
2. Description of the Related Art
There is an ink jet recording system in which by rapidly vaporizing a predetermined amount of ink by heat, which heat is created by a heater resistor, an ink drop is then ejected from a orifice by such a resultant vapor bubble. In this system, the heater resistor tends to corrode due to the heat and the ink. In order to prevent this, an ink protection layer is interposed between the heater resistor and the ink. As a result of the ink protection layer, which covers the heater resistor, and through which the ink is heated, thermal conductivity with respect to the ink declines. In consideration of this defect, there is a measure in which a surface of a heater resistor is oxidized to form a surface oxidation film, and then, such a resultant surface oxidation film is utilized as an ink protection layer. This surface oxidation film is generally extremely thin, and thus, has good thermal conductivity with respect to the ink. An ink jet recording head is known, using heater resistors that are made from a material, such as TaSiO. Surfaces of the heater resistors are oxidized, so that such resultant oxidation surfaces each can serve as an ink protection layer (for example, refer to Japanese Patent Application Laid-Open (JP-A) No. 10-230605).
However, in a head structure in which heater resistors, each of which is made from, for example, TaSiO and has an oxidized surface layer serving as an ink protection layer, are used, major part of an insulating film layer is generally covered with the ink protection layers (or the oxidized surfaces) of the heater resistor and the remaining part or some part of the insulating film layer is not covered, i.e., it is exposed to the outside. The insulating film layer is ordinarily made from a silicon insulator, which is easily corroded by thermochemical reaction depending upon a composition of the ink. Therefore, some type of material to be used as the ink, which material does not corrode such a silicon insulator, must be selected from a limited number of such materials. As a result, the versatility of an ink jet recording head cannot be increased, so as to allow use of a wide variety of ink.
Further, to prevent the ink from corroding the silicon insulator, it is necessary to further provide an additional ink protection layer for covering the silicon insulator. In this case, as previously described, because the ink is heated purposely through this additional ink protection layer, thermal conductivity with respect to the ink declines.